Dispersions containing perfluorovinyl ether homopolymers and use thereof

ABSTRACT

The present invention provides a method of preparing an aqueous dispersion of poly(perfluorovinyl ether)homopolymers. The present invention further relates to a method of making an aqueous fluoropolymer dispersion comprising bicomponent particles of poly(perfluorovinyl ether)homopolymers and a second fluoropolymer. The dispersions of the present invention may be used for rendering fibrous substrates oil repellent, water repellent and/or stain repellent.

FIELD OF THE INVENTION

[0001] The present invention relates to a method of preparing an aqueousdispersion of poly(perfluorovinyl ether)homopolymers. The presentinvention further relates to a method of making an aqueous fluoropolymerdispersion comprising bicomponent particles of poly(perfluorovinylether)homopolymers and a second fluoropolymer. The dispersions of thepresent invention may be used for rendering fibrous substrates oilrepellent, water repellent and/or stain repellent. The invention furtherrelates to fibrous substrates, in particular textiles, treated with thefluorochemical composition and to a method of treating the fibroussubstrate with the fluorochemical dispersions.

BACKGROUND

[0002] Compositions for making substrates, in particular fibroussubstrates, such as textiles, oil and water repellent have been longknown in the art. When treating fibrous 20 g substrates and inparticular textile such as apparel, it is a requirement that the textileretains its look and feel as much as possible. Therefore, the amount ofcomposition that can be applied in any treatment to provide repellencyproperties to the substrates is limited because large amounts wouldresult in disturbing the look and feel of the substrate and would makethem useless for many applications. As a result, the composition usedfor treating the substrates need to be effective at low applicationlevels.

[0003] Fluorochemical compounds have been well known as being highlyeffective in providing oil and water repellency to substrates and inparticular textile substrates. The commercially available fluorochemicalcompositions can be applied at low levels and are generally effective inproviding the desired oil and water repellency properties at these lowlevels.

[0004] Fluorochemicals taught for treating textile include polymersbased on vinyl ethers that have a perfluoroalkyl group. For example,U.S. Pat. No. 4,929,471 discloses the use of a copolymer of CH₂═CH—ORwherein R may represent a fluorinated group for treating polyesterfabric during its manufacturing process so as to produce a polyesterfabric that has similar physical properties as silk or rayon.

[0005] U.S. Pat. No. 4,029,867 discloses to provide soil repellency andsoil release properties to textile using a copolymer of maleic anhydrideand a comonomer of the formula CH₂═CH—CH₂—O—R_(f) wherein R_(f)represents a perfluorinated group. A homopolymer of CH₂═CH—O—R_(f) isdisclosed in DE 1720799 and is mentioned to be suitable for renderingtextile oil and water repellent. The aforementioned fluorochemicalcompositions are all based on fluorine containing polymers that do nothave a fluorinated backbone.

[0006] Fluoropolymers having a fluorinated backbone such as for examplepolytetrafluoroethylene (PTFE) and copolymers of tetrafluoroethylene(TFE), have been known for coating substrates to provide variousproperties to the substrate including repellency properties.Fluoropolymers have for example been coated on cookware to providedesired release properties thereto. Fluoropolymers having a fluorinatedbackbone are disclosed in U.S. Pat. No. 4,546,157, U.S. Pat. No.4,619,983, U.S. Pat. No. 4,766,190, U.S. Pat. No. 5,110,385, U.S. Pat.No. 5,969,066, U.S. Pat. No. 3,450,684, U.S. Pat. No. 4,035,565, U.S.Pat. No. 4,368,308, U.S. Pat. No. 4,418,186, U.S. Pat. No. 4,654,394,U.S. Pat. No. 4,840,998, U.S. Pat. No. 5,639,838 and U.S. Pat. No.3,136,745. However, to be effective as a repellent coating, it has beentaught to apply fluoropolymer coatings in high amounts. Such thickcoatings are however unsuitable for treating textiles as they change thelook and feel of the textile substrate substantially, i.e. to the extentsuch textiles are unsuitable for use in apparel. Sometimes, suchcoatings are subsequently subjected to a sintering step at hightemperatures that would generally destroy many of the fibrous substratesdesired for treatment.

[0007] EP 969 055 for example discloses an aqueous dispersion containingPTFE and a copolymer of TFE and a perfluorovinyl ether (PVE) for coatingsubstrates such as ceramics or to impregnate textile. However, theamount of fluoropolymer in the treatment solution is at least 25% byweight resulting in a fairly thick coating. Moreover, the coating issubjected to a sintering step at a temperature of 420° C. which woulddestroy many fibrous materials used for apparel.

[0008] U.S. Pat. No. 4,670,328 discloses aqueous dispersions of certaincopolymers of TFE and PVE for the impregnation of textiles. Again, thelevel of fluoropolymer applied in the impregnation is so large that thelook and feel of the textile is substantially affected. Accordingly, theimpregnated materials are generally only useful in specializedapplications such as dust free clothes or chemical resistant clotheswhere the appearance of the clothes is of secondary consideration.

[0009] EP 186186 discloses a curable fluoroolefin polymer for makingcoatings that have high weatherability and good repellency propertiessuch as water repellency, oil repellency and/or stain repellency.However, a thick coating is apparently required to achieve theseproperties.

[0010] Fluorochemical compositions for rendering fibrous substrates oil-and/or water repellent are described in Applicant's co-pendingapplication U.S. Ser. No. 09/861,782 filed May 21, 2001. Thecompositions comprise up to 4% by weight of a fluoropolymer having afully- or partially fluorinated backbone and comprise repeating units ofthe formula —CF₂—CFR_(f)—, where R_(f) is a perfluorinated organic grouphaving a chain length of at least two atoms and having at least onecarbon atom.

[0011] Although perfluorovinyl ether homopolymers have been prepared,and copolymers of perfluorovinyl ethers have been used in textiletreatments, the difficulty in preparing perfluorovinyl etherhomopolymers have heretofore prohibited their use in textile treatments.It would thus be desirable to find alternative fluorochemicalcompositions that do not display many of the disadvantages of thefluorochemical compositions in the prior art. In particular, it would bedesirable to find fluorochemical compositions comprising perfluorovinylether homopolymers that are effective in providing oil and waterrepellency to a fibrous substrate, in particular a textile substrate,without substantially adversely affecting the appearance of the textile,i.e. such that the fibrous substrate is suitable for use in apparel.Preferably, the fluorochemical compositions are also capable ofproviding soil repellency and soil release properties to the fibroussubstrate. Desirably, the fluorochemical compositions will be moreenvironmental friendly and sufficiently stable to substantially avoidformation of low molecular weight fluorinated substances. Thefluorochemical compositions are preferably also compatible with commonlyused textile treatments and are preferably easy to apply by a customerin a reproducible and reliable way. Finally, the desired fluorochemicalcompositions are preferably capable of providing durable repellencyproperties to a fibrous substrate.

SUMMARY OF THE INVENTION

[0012] The present invention provides a method of making apoly(perfluorovinyl ether) homopolymer dispersion comprising the stepsof:

[0013] a) pre-emulsifying an aqueous mixture of a perfluorovinyl etherin the presence of a fluorochemical emulsifier to an average emulsiondroplet size of 1 micron or less, and

[0014] b) polymerizing said perfluorovinyl ether in the presence of afree-radical initiator at temperature and for a time sufficient toproduce particles of poly(perfluorovinyl ether).

[0015] The perfluorovinyl ether used in the present invention of claim 1are of the formula: CF₂═CF—R_(f,) wherein R_(f) represents aperfluorinated organic group having a chain length of at least 2 atomsand having at least one carbon atom and one oxygen atom. The R_(f) groupmay be a perfluoroalkoxy group, a perfluoroether group or aperfluoropolyether group.

[0016] The present invention further provides a method of making afluoropolymer dispersion comprising bicomponent particles comprising thesteps of:

[0017] a. pre-emulsifying an aqueous mixture of a perfluorovinyl ethermonomer in the presence of a fluorochemical emulsifier to an averageemulsion droplet size of one micron or less, and

[0018] b. polymerizing said perfluorovinyl ether in the presence of afree-radical initiator at temperature and for a time sufficient toproduce particles of poly(perfluorovinyl ether),

[0019] c) subsequently adding at least one additional fluorinatedco-monomer without additional fluorochemical emulsifier, and

[0020] d) further polymerizing the resulting mixture.

[0021] As used herein a “bicomponent particle” is a single particle oftwo distinct fluoropolymers. The first fluoropolymer is a homopolymer ofone or more perfluorovinyl ether monomers. The second fluoropolymer maybe any fluoropolymer comprising one or more fluoromonomers, such astetrafluoroethylene homo- or copolymers, vinylidene fluoride homo- orcopolymers, or hexafluoropropylene homo- or copolymers or perfluorovinylether homo- or copolymers. The bicomponent particle may comprise acore-shell, inverted core-shell, half-moon, or other morphologies.

[0022] In a further aspect, the present invention provides afluoropolymer dispersion for rendering a fibrous substrate oil and/orwater repellent. The fluorochemical dispersion may comprise particles ofpoly(perfluorovinyl ether) homopolymer or may comprise bicomponentparticles of poly(perfluorovinyl ether) homopolymer and a secondcomponent fluoropolymer.

[0023] In a still further aspect, the invention relates to afluoropolymer dispersion that comprises a bicomponent particlecomprising a first poly(perfluorovinyl ether) and a secondfluoropolymer. The first fluoropolymer consists essentially of repeatingunits corresponding to the general formula:

[0024] wherein R_(f) represents a perfluorinated organic group having achain length of at least 1 oxygen atom and having at least one carbonatom.

[0025] Such dispersions of bicomponent particles have been found to beparticularly effective for the treatment of fibrous substrates. Inparticular it was found that the second fluoropolymer contributed to animprovement of the repellency properties often going beyond a mereaddition of the oil repellency properties of the fluoropolymers on theirown, particularly with an auxiliary component as described below.Accordingly, the cost of a fluorochemical treatment composition maythereby be lowered as the cost of the first poly(perfluorovinylether)homopolymer is generally higher than that of the secondfluoropolymer.

[0026] The fluoropolymer dispersion of the present invention has beenfound to be effective for providing oil repellency and/or waterrepellency properties to a fibrous substrate without substantiallyaffecting the appearance thereof. Furthermore, the fluoropolymerdispersion may be produced such that the amount of low molecular weightspecies (less than 1000 g/mol) in the composition is low, e.g. not morethan 0.5% by weight, preferably not more than 1000 ppm, or is even freeof such substances. Also, the fluoropolymer dispersions generally willhave a high chemical stability such that the fluoropolymer dispersionsgenerally do not form low molecular weight fluorinated substances over along period of time. The fluoropolymer dispersion may further providesoil repellency as well as soil or stain release properties. With theterm soil and stain release is meant that a treated substrate thatbecomes soiled or stained can be more easily cleaned in for example ahome laundering than an untreated substrate that becomes soiled orstained. Soil/stain repellency on the other hand refers to the abilityto repel soil thereby reducing soiling or staining of the substrate.

[0027] The amount of the fluoropolymer in a treatment composition willtypically be selected in order to achieve the desired level offluoropolymer on the substrate to be treated. Typically the amount ofthe fluoropolymer in the treatment composition is not more than 4% byweight (based on the total weight of the composition), for examplebetween 0.01% by weight and 4% by weight, preferably between 0.05% and3% by weight. Higher amounts of the fluoropolymer can be used as well,particularly in cases where the uptake of the composition by the fibroussubstrate is low.

[0028] In a further aspect, the present invention relates to a treatmentof fibrous substrates with the above fluorochemical compositions. Thesubstrates so obtained generally have good repellency properties such asoil repellency, water repellency, soil repellency. Additionally, thetreated substrates may exhibit good or improved soil/stain releaseproperties as well.

[0029] In a still further aspect of the present invention there areprovided fibrous substrates, in particular textiles, that have coated onat least part of at least one major surface, the fluoropolymerdispersion of the invention. The amount of the fluoropolymer on such atreated fibrous substrate should generally be less than 3% by weightbased on the weight of the fibrous substrate so as to preserve thegeneral look and feel of the substrate although the amount that can beapplied without adversely affecting the look and feel of the substratewill depend on the nature of both the substrate as well as thefluorochemical composition used in the treatment.

[0030] In yet another aspect, the invention relates to the use of afluoropolymer dispersion to impart oil repellency, water repellency,soil repellency and/or soil/stain release to a fibrous substrate withoutsubstantially affecting the look and feel of said fibrous substrate, thefluorochemical composition comprising a solution or dispersion of afluoropolymer having fully fluorinated backbone and comprising one ormore repeating units corresponding to the general formula:

[0031] wherein R_(f) represents a perfluorinated organic group having achain length of at least 1 oxygen atom and having at least one carbonatom. By the term “without substantially affecting the look and feel ofsaid fibrous substrate” is meant that the treated substrate does notdiffer substantially in appearance from the untreated substrate suchthat the treated substrate can be used without objection in applicationssuch as for example apparel, where the look and feel of the fibroussubstrate are a major consideration for its use.

[0032] Finally, the invention relates to fluorochemical compositionsthat comprise a dispersion of the aforementioned fluoropolymer(s) andfurther an auxiliary component, generally a non-fluorinated organiccompound, that is capable of further improving the water and/or oilrepellency and/or the soil/stain release properties of a fibroussubstrate treated with the fluorochemical composition.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS OF THE INVENTION

[0033] Fluoropolymers for Use in the Fluorochemical Composition

[0034] The poly(perfluorovinyl ethers) for use in the fluorochemicalcomposition are polymers that have a fully fluorinated backbone. Theterm “fully fluorinated” includes polymers in which all hydrogen atomson the backbone have been replaced by fluorine as well as polymers inwhich all hydrogen atoms on the backbone have been replaced withfluorine and chlorine or bromine.

[0035] The fluoropolymer has one or more repeating units that correspondto the general formula:

[0036] wherein R_(f) represents a perfluorinated (i.e. all hydrogenatoms have been replaced by fluorine atoms) organic group having a chainlength of at least 1 oxygen atom and including at least one carbon atom.Preferably the chain length of the perfluorinated organic group is atleast 3 atoms. A particularly preferred R_(f) group has a chain lengthof at least 4 atoms of which at least 3 are carbon atoms.

[0037] Examples of R_(f) groups include perfluorinated aliphatic groupsthat contain one or more oxygen atoms. The R_(f) group may in particularbe a linear or branched perfluoralkoxy group, preferably, theperfluoroalkoxy group will have between 1 and 6 carbon atoms andspecific examples include perfluorinated methoxy, ethoxy and n-propoxygroups. Still further, the R_(f) group can be a perfluoropolyether whichmay be linear or branched. According to a preferred embodiment, theR_(f) group corresponds to the following general formula:

—O(R¹ _(f)O)_(n)(R² _(f)O)_(m)R³ _(f)   (II)

[0038] wherein R¹ _(f), R² _(f) each independently represents a linearor branched perfluoroalkylene group having 1, 2, 3, 4, 5 or 6 carbonatoms, R³ _(f) represents a linear, branched or cyclic perfluoroalkylgroup having 1, 2, 3, 4, 5 or 6 carbon atoms and n and m eachindependently represents an integer of 0 to 10. Preferably, at least oneof n and m is different from 0. Particularly preferred R_(f) groupsaccording to formula (II) include those in which m is 0, n is 1, R¹ _(f)is —CF₂CF₂—, —CF₂CF(CF₃)—, —CF(CF₃)CF₂— or —CF₂CF₂CF₂— and R³ _(f)represents a linear, branched or cyclic perfluoroalkyl group having 1 to6 carbon atoms. A preferred R_(f) groups according to formula (II)includes in particular a perfluoropropyl group and those in which both mand n are 0. Another preferred R_(f) group according to formula (II)includes in particular a perfluoropropyl group and those in which thesum of m and n is 1.

[0039] It will be understood by one skilled in the art that thefluoropolymer of the fluorochemical composition may comprise a mixtureof repeating units according to formula (I). For example, thefluoropolymer may comprise a mixture of repeating units in which theR_(f) groups correspond to formula (II) above such as for example amixture of a repeating unit corresponding the formula:

[0040] and a repeating unit corresponding to the formula:

[0041] or a mixture of repeating units derived from a combination ofperfluoro(propyl vinyl) ether and a monomer of the formulaCF₂═CF—O—CF₂CF(CF₃)—O—CF₂CF₂CF₃.

[0042] The repellency properties that can be achieved by thefluorochemical composition largely depend on the presence in thefluoropolymer of perfluorovinyl ether repeating units according toformula (I). A fluoropolymer containing only repeating units accordingto general formula (I) has been found to yield excellent repellencyproperties on a fibrous substrate treated therewith. Although higheramounts of the repeating units of formula (I) will generally improveperformance, the cost of the fluoropolymer thereby also increases aswell because the monomers from which these repeating units are derivedare generally expensive.

[0043] In a particular embodiment of the present invention, thefluorochemical composition comprises a fluoropolymer dispersioncomprising bicomponent particles of a first poly(perfluorovinylether)homopolymer and second fluoropolymer each having a fully- orpartially fluorinated backbone. It is believed that the bicomponentparticles are a core-shell polymer comprising a core ofpoly(perfluorovinyl ether)homopolymer and a shell of a secondfluoropolymer.

[0044] The first fluoropolymer consists essentially of one or morerepeating units corresponding to the general formula (I) set forthabove. Generally the second fluoropolymer contains the repeating unitsof formula (I) in a total amount of not more than 50 mole %. The amountof repeating units in the second fluoropolymer may even be less, forexample not more than 25 mole % or not more than 10 mole %. Further,even if less than 1 mole % or substantially no repeating units arepresent in the second polymer, beneficial effects of the second polymerhave been noticed. In particular, it was noticed that although thesecond fluoropolymer generally does not (e.g. if it does not contain therepeating units of formula (I)) or only to a limited extent providesrepellency properties when used on its own, the second fluoropolymer isnevertheless capable of improving the repellency performance when usedin a dispersion of bicomponent particles with the first fluoropolymer.

[0045] Generally, any ratio of first to second fluoropolymers can beused to prepare the emulsion and the optimal ratio will depend on thenature of the fluoropolymers used in the mixture, the nature of thefibrous substrate, amount of the mixture applied and level of repellencydesired. The optimal ratio can easily be determined through routineexperimentation. Generally, the weight percent of the firstfluoropolymer will be between 1 to 50 wt. %, preferably between 1 to 30wt. %, with the second fluoropolymer providing the balance. Thus,mixtures that are rich in the second fluoropolymer (have a weightpercent of second fluoropolymer of 50% or more), which contains no orlittle of the repeating units of formula (I), have been found to yieldgood repellency properties. Generally however, the total amount ofrepeating units according to the general formula (I) in such mixturesshould be at least 10 wt. %, preferably at least 20 wt. % to achievegood levels of repellency.

[0046] The bicomponent or core-shell particle dispersion may be preparedby the steps of:

[0047] 1) polymerizing an aqueous emulsion of monomers of the formula:

CF₂═CF—R_(f),

[0048] wherein R_(f) represents a perfluorinated organic group having achain length of at least 2 atoms and having at least one carbon atom andone oxygen atom;

[0049] in the presence of a free radical initiator and a emulsifier attemperature and for a time sufficient to produce particles ofpoly(perfluorovinyl ether),

[0050] 2) subsequently adding at least one additional fluorinatedco-monomer without additional fluorochemical emulsifier, and

[0051] 3) further polymerizing the resulting mixture.

[0052] Preferably, the emulsion of step 1) comprises droplets having anaverage droplet size of less than 1 micron, preferably 300 nanometers.

[0053] An important benefit of the use of a fluoropolymer mixture isthat the total cost of the treating composition can be reduced whilestill achieving a high level of performance, as the cost ofperfluorovinyl ether monomers considerably exceeds that of othermonomers that may be used in the second stage of the polymerizationprocess.

[0054] The second fluoropolymer component of the bicomponent particlecomprises a homo or copolymer of at least one ethylenically-unsaturatedfluoromonomer containing at least one fluorine atom substituent on adouble-bonded carbon atom, and further substituted with a halogen atomsuch as fluorine, chlorine, or bromine; hydrogen, or a lower fluoroalkylradical.

[0055] Useful fluorinated comonomers of the second componentfluoropolymer include homo- and copolymers of tetrafluoroethylene,vinylidene fluoride, hexafluoropropene, chlorotrifluoroethylene,2-chloropentafluoropropene, 1-hydropentafluoropropene,dichlorodifluoroethylene, trifluoroethylene, 1,1-chlorofluoroethylene,trichloroethylene, and the like and optionally a monomer correspondingto formula (1) above.

[0056] Generally, the fluoropolymer will contain between 0 and 70 mole%, preferably between 0 and 60 mole %, more preferably between 0 and 40mole % of repeating units derived from tetrafluoroethylene, between 0and 95 mole %, preferably between 20 and 80 mole %, more preferablybetween 30 and 75 mole % of repeating units derived from vinylidenefluoride, between 0 and 95 mole %, preferably between 20 and 80 mole %,more preferably between 30 and 75 mole % of repeating units derived fromhexafluoropropene, whereby the total amount of repeating units derivedfrom vinylidene fluoride, hexafluoropropene and tetrafluoroethylene isgenerally between 0 and 95 mole %, preferably between 20 and 90 mole %,more preferably between 30 and 90 mole %.

[0057] The second component fluoropolymer of the fluorochemicalcomposition contain further repeating units derived from non-fluorinatedmonomers. Examples of non-fluorinated monomers include alpha-olefinhydrocarbons such as ethylene and propylene. The amount of such furtherrepeating units may vary widely and can be from 0 mole % to 50 mole %for any particular non-fluorinated monomer.

[0058] Specific examples of second component fluoropolymers that can beused in the fluorochemical composition of this invention are copolymersof tetrafluoroethylene and a perfluorovinyl ether such asperfluoro(methyl vinyl)ether, perfluoro(methoxyethyl vinyl)ether,perfluoro (propyl vinyl)ether (PPVE-1), perfluoro (2-(n-propoxy)propylvinyl)ether(PPVE-2) and perfluoro(ethoxyethyl vinyl)ether, copolymers oftetrafluoroethylene, hexafluoropropylene and a perfluorovinyl ether suchperfluoro(methyl vinyl)ether, perfluoro(methoxyethyl vinyl)ether,PPVE-1, PPVE-2 and perfluoro(ethoxyethyl vinyl)ether, copolymers ofvinylidene fluoride and a perfluorovinyl ether such as perfluoro(methylvinyl)ether, PPVE-1, PPVE-2, perfluoro(methoxyethyl vinyl)ether andperfluoro(ethoxyethyl vinyl)ether, copolymers of vinylidene fluoride,tetrafluoroethylene and a perfluorovinyl ether such as perfluoro(methylvinyl)ether. perfluoro(methoxyethyl vinyl)ether, PPVE-1, PPVE-2, andperfluoro(ethoxyethyl vinyl)ether, copolymers of vinylidene fluoride,hexafluoropropylene and a perfluorovinyl ether such as perfluoro(methylvinyl)ether, PPVE-1, PPVE-2, perfluoro(methoxyethyl vinyl) ether andperfluoro(ethoxyethyl vinyl)ether and copolymers of vinylidene fluoride,tetrafluoroethylene, hexafluoropropylene and a perfluorovinyl ether suchas perfluoro(methyl vinyl)ether, PPVE-1, PPVE-2, perfluoro(methoxyethylvinyl)ether and perfluoro(ethoxyethyl vinyl)ether.

[0059] Method of Making the Fluoropolymers

[0060] The poly(perfluorovinyl ether)homopolymer particles are producedthrough aqueous emulsion polymerization of a pre-emulsion comprising theperfluorovinyl ether monomer and fluorinated emulsifier wherein theaverage droplet size of the pre-emulsion is one micron or less,preferably 300 nanometers or less. In the aqueous emulsionpolymerization, the monomers are polymerized in the aqueous phase in thepresence of a free radical initiator and a fluorinated emulsifier,preferably a non-telogenic emulsifier.

[0061] Generally the time required for the homopolymerization is 6 toabout 48 hours and the temperatures ranges from 40 to 80° C., preferably40 to 60° C. Higher temperatures may lead to destabilization of thedroplets.

[0062] The fluorochemical emulsifier will generally be used in amountsless than 1% by weight, for example from 0.1 to 1% by weight based onthe weight of the aqueous phase. Examples of fluorinated emulsifiersinclude salts, in particular ammonium salts of linear or branchedperfluoro alkyl containing carboxylic and sulphonic acids having 4 to 11carbon atoms in the alkyl chain. Specific examples includeperfluorooctanoic acid ammonium salt (APFO, described in U.S. Pat. No.2,567,011) C₈F₁₇SO₃Li which is commercially available from Bayer AG,C₄F₉SO₃Li and C₄F₉SO₃K (described in U.S. Pat. No. 2,732,398). A furtherexample of a perfluoroalkyl containing carboxylic acid salt isC₈F₁₇SO₂N(C₂H₅)CH₂COOK (described in U.S. Pat. No. 2,809,990). Stillfurther emulsifiers that can be used includeperfluoropolyethercarboxylate emulsifiers such as disclosed in EP 219065

[0063] In accordance with an embodiment of the present invention, theemulsion polymerization may be conducted using a fluorinated emulsifierhaving a molecular weight of at least 200 g/mol, preferably at least1000 g/mol for example by using a polymeric fluorinated emulsifier.Examples of suitable fluorinated polymeric or high molecular weightemulsifiers include perfluoropolyethers having one or more hydrophilicgroups, in particular ionic groups such as carboxylic acid groups orsalts thereof. Examples of perfluoropolyether emulsifier include thoseaccording to the following formulas (IV) or (V):

R^(f) _(a)—O—(CF₂O)_(k)(CF₂CF₂O)_(p)(CF(CF₃)CF₂O)_(q)-Q¹-COOM   (IV)

MOOC-Q¹-O—(CF₂O)_(k)(CF₂CF₂O)_(p)(CF(CF₃)CF₂O)_(q)-Q²-COOZ   (V)

[0064] wherein k, p and q each represent a value of 0 to 15, typically 0to 10 or 12 and the sum of k, p and q being such that the averagemolecular weight is at least 200 g/mol, preferably at least 100 g/mol,R_(f) ^(a) represents a perfluoroalkyl group of 2 to 4 carbon atoms, Mand Z each independently represent hydrogen or a cation, preferably amonovalent cation such as ammonium or an alkali metal ion and Q¹ and Q²each independently represents —CF₂— or —CF(CF₃)—.

[0065] Examples of fluorinated compounds useful as emulsifiers offormula (IV) include those corresponding to the general formula:

R_(f) ^(a)—O—(CFXCF₂O)_(r)—CFX—COOM   (VI)

[0066] wherein R_(f) ^(a) and M have the meaning as defined in formula(IV), X is a hydrogen atom or a fluorine atom and r has a value of 2 to15. Examples of such fluorinated emulsifiers are disclosed in EP 219065.Commercially available fluorinated compounds according to formula (IV)or (V) include FLUOROLINK™ C available from Ausimont SpA, KRYTOX™ 157FSL, KRYTOX™ 157 FSM and KRYTOX™ 157 FSH, all available from E. I.Dupont de Nemours and Company.

[0067] Still further fluorinated polymeric compounds useful asemulsifiers include the perfluoropolymers that comprise repeating unitsderivable from a monomer of the formula:

[0068] wherein s is 0, 1 or 2, and t is an integer of 2 to 4, and G is amoiety containing one or more hydrophilic groups, such as a nonionic,anionic or cationic group. Examples of suitable nonionic groups include:—SO₂F; hydroxyalkylene, e.g., —(CH₂)_(n)OH where n is an integer of 1 to18; hydroxyarylene; and an ester, e.g., —COOR, wherein R is an alkylgroup of 1 to 3 carbon atoms. Examples of suitable anionic groupsinclude: carboxyl groups, e.g., —CO₂M where M may be hydrogen, a mono ordivalent metal ion (e.g., sodium, potassium or magnesium), ammonium(e.g., simple ammonium, tetraalkylammonium, tetraarylammonium) orphosphonium (e.g., tetraalkylphosphonium); or sulfonate groups, e.g.,—SO₃M, where M is defined as above. Examples of suitable cationic groupsinclude alkylammonium groups, (e.g., —(CH₂)_(n)NR₃ ⁺Cl⁻ where R may behydrogen, alkyl or aryl).

[0069] Preferably, the fluorinated polymeric emulsifier is a copolymerof tetrafluoroethylene and a monomer according to formula (VII). Suchcopolymers and their method of making are disclosed in for example U.S.Pat. No. 5,608,022 and WO 00/52060. Suitable fluorinated polymericcompounds useful as emulsifiers are available as Nafion™ superacidcatalysts (e.g., Nafion™ SE10172) from E. I duPont de Nemours & Co.,Wilmington, Del. and are also available as Flemion™ superacid polymersfrom Asahi Chemical Co., Osaka, Japan and as Acipex™ superacid polymersfrom Asahi Glass Co., Tokyo, Japan.

[0070] If desired, several methods may be used to recover and recyclethe fluorinated emulsifiers used in the aqueous emulsion polymerization.Such methods are disclosed in e.g. EP 524585, EP 566974, EP 632009, EP731081, WO 99/62858, WO 99/62830 and DE 19932771. Any of these methodsmay advantageously be practiced in this invention to remove and orminimize any remaining fluorinated emulsifier subsequent to the emulsionpolymerization.

[0071] According to a particular embodiment for making the fluoropolymerdispersions, the liquid perfluorovinyl ether monomer used in thepolymerization is pre-emulsified prior to its homopolymerization. Thepresent method allows the preparation of perfluorovinyl etherhomopolymers much more efficiently than the processes of the prior art.By the term “pre-emulsified” in connection with the present invention ismeant that the fluorinated monomer is emulsified in water to a dropletsize of one micron or less, preferably 300 nm or less, with the aid ofthe fluorinated emulsifier prior to polymerization of the liquidfluorinated monomer. The temperature of the polymerization to prepare anemulsion of perfluorovinyl ether homopolymer is generally between 40 and100° C., preferably between 50 and 80° C.

[0072] The perfluorovinyl ether monomer can be emulsified in water withthe aid of a fluorinated emulsifier such as described above, prior toits polymerization with the other monomers. The pre-emulsification ofthe liquid fluorinated monomer results in an emulsion having monomerdroplets. The pre-emulsion average droplet size can range from anaverage diameter of 1 μm or less, down to about 150 nm or even lower.Preferably the average droplet diameter is not more than 300 nm. Theaqueous emulsion should preferably have a pot life (settling time) of atleast 1 hour, more preferably at least 3 hours. The pot life or settlingtime is defined as the time required for 10% by weight of the monomerdroplets to settle or separate out of the aqueous emulsion. Droplet sizemay be determined, for exampled, by light scattering experiments as areknown in the art.

[0073] Aqueous emulsions of the perfluorovinyl ether monomer canconveniently be obtained by suitable emulsification equipment such asfor example high speed rotor-stator mixers such as an Ultra-Turrax(Ika). The stirring rates should be sufficiently high to achieve thedesired degree of emulsification and stability. Generally, stirringrates of 24000 rpm or more can be employed. Air is preferably excludedduring the emulsification. The pre-emulsion particle size can be furtherreduced with high pressure homogenizers, available from APV Gaulin orMicrofluidics.

[0074] The amount of fluorinated emulsifier used to emulsify liquidfluorinated monomer is generally between 0.01 and 15% by weight based onthe weight of the liquid fluorinated monomer, preferably 0.1 to 4% byweight. Although higher amounts of emulsifier can be used, they will notnecessarily lead to a significant increased pot life of the aqueousemulsion of liquid fluorinated monomer produced. In the two-step processfor making the bicomponent particle emulsion, lesser amounts my be used.

[0075] In the two-stage process of the invention, where a dispersion ofbicomponent particles are prepared, the pre-emulsion is firstpolymerised to a degree of conversion of at least 1%, preferably atleast 5%, as described, to produce a dispersion of perfluorovinyl etherhomopolymer particles and unconverted perfluorovinyl ether monomer (ifany). Additional fluorinated monomers are added with continuousagitation while the second stage of polymerization proceeds. The secondstage of polymerization should occur without additional fluorinatedemulsifier. In the absence of additional emulsifier, a bi-componentparticle dispersion is produced and the additional charge of fluorinatedmonomers are polymerized on the surface of the perfluorovinyl etherhomopolymer particles. Were additional fluorinated emulsifier to beadded, a mixture of discreet particles would be produced; a firstparticle of perfluorovinyl ether homopolymer and a second particle offluoropolymer derived from the additional fluorinated monomer feed atthe second stage of polymerization.

[0076] In the two-stage polymerization process (to produce thebicomponent dispersion) the polymerization may be initiated at a firsttemperature for the first stage of polymerization and at a secondtemperature for the second stage of polymerization. The initial periodwill typically be between 1 and 6 hours, for example between 1 and 4hours from the start of the polymerization reaction. If desired, furtherinitiator may be added during the polymerization but this may not berequired. Amounts of initiator in the initial charge are generallybetween 0.01 and 2.0% by weight, preferably between 0.1 and 1.8% byweight, more preferably between 0.3% and 1.6% by weight based on thetotal weight of polymer to be produced. The temperature for use at theinitial stage (when a higher temperature is used) is generally between40° C. and 100° C., preferably between 50° C. and 80° C. The temperatureduring the course of polymerization is generally in the range of 30° C.to 80° C. The optimal conditions can be readily determined by routineexperimentation.

[0077] Actinic radiation may be used, instead of free radicalinitiators, to initiate the polymerization. When actinic radiation, suchas UV, is used to initiate the polymerization, lower temperatures fromabout 0° C. to ambient may used.

[0078] The aqueous emulsion polymerization of the perfluorovinyl ethercan be carried out continuously in which, for example, a pre-emulsion ofperfluorovinyl ether monomers, water, fluorochemical emulsifiers,buffers and initiators are fed continuously to a stirred reactor underoptimum pressure and temperature conditions while the resultingdispersion or suspension is removed continuously. An alternativetechnique is batch or semibatch (semi-continuous) polymerization byfeeding a pre-emulsion of the ingredients into a stirred reactor andallowing them to react at a set temperature for a specified length oftime until a desired amount of polymer is formed.

[0079] In the second stage of the polymerization, the dispersion ofpoly(perfluorovinyl ether) is provided with the additionalfluoromonomers in a continuous or batch mode.

[0080] The polymerization can be carried out in a standard orconventional vessel used for emulsion polymerization, but a pressurevessel is generally required for the second stage where gaseousfluorinated monomers are charged.

[0081] For the free-radical polymerization use may be made of anysuitable initiator or any suitable initiator system, for exampleammonium persulfate (APS), or of redox systems, such as APS/bisulfite,potassium permanganate or actinic radiation such as UV light. Ifoil-soluble initiators are used in the polymerization, it is generallypreferred for these to be mixed with the aqueous emulsion of theperfluorovinyl ether monomer. For the purposes of the present invention,oil-soluble initiators are those which have no, or only insufficient,solubility in water. Examples of oil-soluble initiators are substituteddibenzoyl peroxides and cumene hydroperoxides, in particularbisperfluoropropionyl peroxide. For the first stage of thepolymerization, persulfates are preferred.

[0082] Water-soluble thermal initiators useful in the present inventionare initiators that, on exposure to heat, generate free-radicals whichinitiate polymerization of the monomers comprising the droplets of theemulsion. Suitable water-soluble thermal initiators include but are notlimited to those selected from the group consisting of potassiumpersulfate, ammonium persulfate, sodium persulfate, and mixturesthereof; and oxidation-reduction initiators such as the reaction productof the above-mentioned persulfates and reducing agents such as thoseselected from the group consisting of sodium metabisulfite and sodiumbisulfite. The preferred water-soluble thermal initiator is ammoniumpersulfate. Preferably, most water-soluble thermal initiators are usedat temperatures of from about 50° C. to about 70° C., while theoxidation-reduction-type initiators are preferably used at temperaturesof from about 25° to about 50° C. Water-soluble thermal initiatorscomprise from about 0.01 to about 2 weight percent, preferably about 0.1to about 2 weight percent based on the total weight of monomers in theemulsion.

[0083] The amount of oxidizing agent added in the initial charge istypically between 10 and 10000 ppm. The amount of reducing agent in theinitial charge is typically also between 10 and 10000 ppm. At least onefurther charge of oxidizing agent and reducing agent is added to thepolymerization system in the course of the polymerization. The furtheraddition(s) may be done batchwise or the further addition may becontinuous.

[0084] The resultant fluoropolymer particles may be used as a dispersionper se. The particles may also be isolated from the aqueous medium byfiltration, coagulation spray drying, extraction into an organicsolvent, or other other techniques such as are known in the art.

[0085] The polymerization systems may comprise auxiliaries, such asbuffers and, if desired, complex-formers or chain-transfer agents.

[0086] Fluorochemical Compositions

[0087] The fluorochemical composition comprises an aqueous dispersion ofthe fluoropolymer (whether perfluorovinyl ether homopolymer particles orthe bicomponent particles). Generally, the amount of fluoropolymercontained in the treating composition is between 0.01 and 4% by weight,preferably between 0.05 and 3% by weight based on the total weight ofthe fluorochemical composition. Higher amounts of fluoropolymer of morethan 4% by weight, for example up to 10% by weight may be used as well,particularly if the uptake of the fluorochemical composition by thesubstrate is low. Generally, the fluorochemical treating compositionwill be prepared by diluting a more concentrated fluorochemicalcomposition to the desired level of fluoropolymer in the treatingcomposition. The concentrated fluorochemical composition can contain thefluoropolymer in an amount of up to 70% by weight, typically between 10%by weight and 50% by weight.

[0088] When the fluorochemical composition is in the form of adispersion in water the volume average particle size of thefluoropolymer particles is generally not more than 300 nm, preferablybetween 50 and 200 nm.

[0089] The dispersion may be additionally stabilized usingnon-fluorinated surfactants, such as non-ionic polyoxyalkylene, inparticular polyoxyethylene surfactants, anionic non-fluorinatedsurfactants, cationic non-fluorinated surfactants and zwitterionicnon-fluorinated surfactants. Specific examples of non-fluorinatedsurfactants that can be used are nonionic types such as Emulsogen EPN207 (Clariant) and Tween 80 (ICI), anionic types such as lauryl sulfateand sodium dodecyl benzene sulfonate, cationic types such as Arquad T-50(Akzo), Ethoquad 18-25 (Akzo) or amphoteric types such as laurylamineoxide and cocamido propyl betaine. The non-fluorinated surfactantis preferably present in an amount of about 1 to about 25 parts byweight, preferably about 2 to about 10 parts by weight, based on 100parts by weight of the fluorochemical composition.

[0090] Alternatively, a solution or dispersion of the fluoropolymers inan organic solvent can be used as the fluorochemical treatingcomposition. Suitable organic solvents include alcohols such asisopropanol, methoxy propanol and t-butanol, ketones such as isobutylmethyl ketone and methyl ethylketone, ethers such as isopropylether,esters such ethylacetate, butylacetate or methoxypropanol acetate or(partially) fluorinated solvents such as HCFC-141b, HFC-134a, HFE-7100,HFE-7200 or perfluoroketones. HFE-7100, HFE-7200 and perfluoroketonesare commercially available from the 3M Company, St. Paul, Minn.

[0091] The fluorochemical composition may contain further additives suchas buffering agent, agents to impart fire proofing or antistaticproperties, fungicidal agents, optical bleaching agents, sequesteringagents, mineral salts and swelling agents to promote penetration. It isparticularly preferred to include one or more auxiliary components otherthan the fluoropolymer and that are capable of further improving theoil- and/or water repellency properties of a fibrous substrate treatedwith the fluorochemical composition or that are capable of improving thesoil/stain release properties of a fibrous substrate treated with thefluorochemical composition. Preferably, the auxiliary components arecapable of improving the durability of the repellency properties and/orsoil/stain release properties.

[0092] The auxiliary components are generally non-fluorinated organiccompounds and are also called extenders hereinafter. Suitable extenderscapable of improving the oil- and/or water repellency properties includefor example blocked isocyanates including aromatic and aliphatic blockedisocyanates, aliphatic polyisocyanates and aromatic or aliphaticcarboduimides including aromatic or aliphatic polycarbodiimides.Auxiliary components that are capable of enhancing the soil/stainrelease properties are generally non-fluorinated organic compounds suchas for example blocked isocyanate compounds that include apolyoxyalkylene group, in particular a polyoxyethylene group. Auxiliarycomponents that are generally capable of improving durability of therepellency properties or soil/stain release properties includenon-fluorinated organic compounds that have one or more groups (or aprecursor thereof) capable of reacting with the surface of the fibroussubstrate. Examples thereof include compounds that have isocyanategroups or blocked isocyanates.

[0093] Method of Treatment of the Fibrous Substrates

[0094] In order to affect treatment of the fibrous substrate the fibroussubstrate is contacted with the fluoropolymer dispersion of theinvention. For example, the substrate can be immersed in thefluorochemical treating dispersion. The treated substrate can then berun through a padder/roller to remove excess fluorochemical compositionand dried. The treated substrate may be dried at room temperature byleaving it in air or may alternatively or additionally be subjected to aheat treatment, for example, in an oven. This heat treatment istypically carried out at temperatures between about 50° C. and about190° C. depending on the particular system or application method used.In general, a temperature of about 120° C. to 170° C., in particular ofabout 150° C. to about 170° C. for a period of about 20 seconds to 10minutes, preferably 3 to 5 minutes, is suitable. Alternatively, thechemical composition can be applied by spraying the composition on thefibrous substrate.

[0095] The amount of the treating composition applied to the fibroussubstrate is chosen so that a sufficiently high level of the desiredproperties are imparted to the substrate surface without substantiallyaffecting the look and feel of the treated substrate. Such amount isusually such that the resulting amount of the fluoropolymer on thetreated fibrous substrate will be between 0.05% and 3% by weight basedon the weight of the fibrous substrate. The amount that is sufficient toimpart desired properties can be determined empirically and can beincreased as necessary or desired.

[0096] Fibrous substrates that can be treated with the fluorochemicalcomposition include in particular textile. The fibrous substrate may bebased on synthetic fibers, e.g. polyester, polyamide and polyacrylatefibers or natural fibers, e.g. cellulose fibers as well as mixturesthereof. The fibrous substrate may be a woven as well as a non-wovensubstrate.

[0097] The invention will now be further illustrated with reference tothe following examples without the intention to limit the inventionthereto. All parts and percentages are by weight unless statedotherwise.

EXAMPLES

[0098] Formulation and Treatment Procedure

[0099] Treatment baths were formulated containing a defined amount ofthe fluoropolymer treatment agent. Treatments were applied to the testsubstrates by padding to provide a concentration as indicated in theexamples (based on fabric weight and indicated as SOF (solids onfabric)). The samples are dried and cured at a temperature of 300° F.for ten minutes. The substrate used for the evaluation of treatments ofthis invention was 100% cotton US-3 :cotton available from Test Fabric,USA. After heat cure, the substrates were tested for their oilrepellency properties.

[0100] Test Method for Oil Repellency (OR)

[0101] The oil repellency of a substrate was measured by the AmericanAssociation of Textile Chemists and Colorists (AATCC) Standard TestMethod No. 118-1997, which test was based on the resistance of a treatedsubstrate to penetration by oils of varying surface tensions aftercontact for 30 seconds. Treated substrates resistant only to Kaydol®mineral oil (the least penetrating of the test oils) were given a ratingof 1, whereas treated substrates resistant to n-heptane (the mostpenetrating, lowest surface tension test liquid) were given a rating of8. Other intermediate values were determined by use of other pure oilsor mixtures of oils, as shown in the following table. A “—” signfollowing a value indicates subjective determination by the rater of avalue intermediate between two values (i.e. 4—indicates a value between3 and 4) Standard Test Liquids AATCC Oil Repellency Rating NumberCompositions 1 Kaydol ® 2 Kaydol ®/n-Hexadecane 65/35 3 n-Hexadecane 4n-Tetradecane 5 n-Dodecane 6 n-Decane 7 n-Octane 8 n-Heptane

[0102] Glossary Table Descriptor Structure and/or Chemical DescriptionAvailability Ammonium (NH₄)₂S₂O₈ Sigma-Aldrich, persulfate Milwaukee, WIFLUOROLINK ™ Perfluoropolyether Ausimont, C macromer functionalizedThorofare, NJ with carboxylic acid groups HFP Hexafluoropropene; Dupont,CF₂═CFCF₃ Wilmington, DE NAFION SE10172 Perfluorosulfonic acid/ DuPont,Polytetrafluorethylene copolymer Wilmington, DE PBS Potassiumperfluorobutanesulfonate 3M, St Paul, MN PPVE-1 Perfluoropropyl vinylether; Matrix Scientific, CF₂═CFOCF₂CF₂CF₃ Columbia, SC PPVE-2Perfluoropropoxypropyl vinyl ether; Can be preparedCF₂═CFOCF₂CF(CF₃)CFOCF₂CF₂CF₃; ˜90% as cited in U.S. Pat. No. 3,450,684(Darby, Ex 1) VDF Vinylidene fluoride; CH₂═CF₂ Sigma-Aldrich, Milwaukee,WI

Example 1

[0103] Preparation of PPVE-2 Homopolymer Dispersion

[0104] FLOUROLINK™ C (3.3 g) and potassium hydroxide (0.186 g) weredissolved in deionized water (90.0 g). To this solution was addedNAFION™ SE10172 (0.0175 g) and PPVE-2 (50.0 g); the resulting aqueousmixture was sonicated for 60 seconds using a Branson 450 sonifier(available from VWR Scientific, Bridgeport, N.J.) to produce a coarseemulsion. The resulting coarse emulsion was then homogenized with aGaulin 15MR homogenizer (available from APV, St. Paul, Minn.) at 8800psi (60.67 MPa) with 3 passes to yield an emulsion with a mean dropletsize of 144 nm. The ensuing fine emulsion was transferred to a 3-neck250 mL round bottom flask, fitted with an overhead stirrer and heatingmantle. A solution of deionized water (10.0 g), sodium bicarbonate(NaHCO₃; 0.2 g) and ammonium persulfate (0.2 g) was added to the stirredmixture. The temperature of the mixture was then elevated and maintainedat 60° C. for 20 hours under a nitrogen blanket. Upon cooling to roomtemperature, the ensuing homopolymer dispersion (characterized usingNMR; 29.1 % solids) yield was determined to be 97.9%, with a meanparticle size of 62 nm as measured on the Horiba LA-910 (HoribaInstruments, Inc, Irvine, Calif.). Monomer conversion to homopolymer was82%.

[0105] Examples 2-4 were prepared essentially according to the procedurefor Example 1, with the exception that the conditions and materialsspecified in Table 1 were used. Resulting % solids, mean particle sizeand conversion to homopolymer for Examples 2-4 are also listed in Table1.

Comparative Example C1

[0106] Comparative Example C1 was prepared essentially according toExample 1 with the exception that the resulting aqueous mixture was notpre-emulsified and duration of the reaction was 24 hours instead of 20hours. TABLE 1 Mean conversion NAFION ™ Temperature particle to homo- ExSE10172 (g) (° C.) Solids (%) size (nm) polymer (%) 1 0.0175 60 29.1 6282 2 — 60 27.7 62 77 3 0.0175 71 28.4 79 80 4 — 71 15.7 87 41 C1* 0.017560 ** — —

Example 5

[0107] Example 5 was prepared essentially according to the procedureused for Example 1 with the exception that FLOUROLINK™ C was replaced byPBS, and the reaction was run at 71° C. for 20 hours. The homopolymerdispersion had a mean particle size of 230 nm with a conversion of 58%.

Example 6

[0108] Example 6 was prepared essentially according to the procedureused for Example 5 with the exception that the addition of NAFION™SE10172 was omitted. The homopolymer dispersion had a mean particle sizeof 157 nm with a conversion of 24%.

Example 7

[0109] Example 7 was prepared essentially according to the procedureused for Example 1 with the exception that PPVE-2 was replaced withPPVE-1. The homopolymer dispersion had a mean particle size of 63 nmwith a conversion of 48%

Example 8

[0110] To deionized water (335.5 g) was added NAFION SE10172 (2.38 g)followed by PPVE-2 (72.0). The ensuing mixture was homogenized using aGaulin 15MR (available from APV, St. Paul, Minn.) at 8800 psi (60.67MPa) for 3 passes, yielding an emulsion which had a mean droplet size of231 nm. To an aliquot of this emulsion (341.6 g) was added a solution ofdeionized water (20.0 g) and ammonium persulfate (1.0 g); the resultingmixture was stirred for several minutes then vacuum charged into a 500mL high pressure reactor fitted with a stirrer, heating mantle,thermocouple, pressure gauge and gas feed valve. After twice purgingwith nitrogen and evacuating, the stirrer was set to 800 rpm and thetemperature of the mixture was brought to 71° C. and maintained for 6hours.

[0111] After 6 hours a 61 wt %/39 wt % VDF/HFP gas mixture wasintroduced into the reactor at 150 psi (1034 kPa). The total gas feedtime into the 500 mL reactor took 3.42 hours. After the gas feed wascomplete, the reactor content was allowed to further react for 2.5hours. Pressure in this time period drops from 150 psi (1034 kPa) toabout 20 psi (138 kPa). The 27.0% solids latex that resulted had a meanparticle size of 112 nm.

Example 9

[0112] The process for Example 9 is essentially the same as Example 8with the exception that the first stage polymerization of the PPVE-2emulsion was allowed to react for 3 hours instead of 6 hours, and theresulting mean particle size of the latex was 82 nm (26.8% solids).

Example 10

[0113] The process for Example 10 is essentially the same as Example 8with the exception that the first stage polymerization of the PPVE-2emulsion was allowed to react for 0.8 hours instead of 6 hours, and theresulting mean particle size of the latex was 127 nm (26.9% solids).

Comparative Example C2

[0114] The process for Comparative Example C2 is essentially the same asExample 8 with the exception that charging of the PPVE-2 emulsion wasimmediately followed by introduction of the VDF/HFP gas mixture, insteadof allowing 6 hours reaction time. The resulting mean particle size ofthe latex was 115 nm (27.7% solids). TABLE 2 Oil repellency values forExamples 8-10 and Comparative Example C2 with varying concentrations oncotton. Hold Time Ex (h) 0.2% SOF 0.5% SOF 1.0% SOF  8 6 1 3 5  9 3 1 3  5− 10 0.8   1−   3− 4 C2 0 0 2   3.5

What is claimed is:
 1. A method of making a poly(perfluorovinyl ether)homopolymer dispersion comprising the steps of: a. pre-emulsifying anaqueous mixture of a perfluorovinyl ether in the presence of afluorochemical emulsifier to an average emulsion droplet size of onemicron or less, and b. polymerizing said perfluorovinyl ether in thepresence of an initiator at temperature and for a time sufficient toproduce particles of poly(perfluorovinyl ether).
 2. The method of claim1 wherein said perfluorovinyl ethers are of the formula: CF₂═CF—R_(f)wherein R_(f) represents a perfluorinated organic group having a chainlength of at least 2 atoms and having at least one carbon atom and oneoxygen atom.
 3. The method of claim 2 wherein said R_(f) group is aperfluoroalkoxy group, a perfluoroether group of a perfluoropolyethergroup.
 4. The method of claim 2 wherein said R_(f) group is of theformula: —O(R¹ _(f)O)_(n)(R² _(f)O)_(m)R³ _(f) wherein R¹ _(f), R² _(f)each independently represents a linear or branched perfluoroalkylenegroup having 1 to 6 carbon atoms, R³ _(f) represents a linear, branchedor cyclic perfluoroalkyl group having 1 to 6 carbon atoms and n and meach independently represents an integer of 0 to
 10. 5. The method ofclaim 4 wherein at least one of n and m is different from
 0. 6. Themethod of claim 4 wherein m is 0, n is 1, R¹ _(f) is —CF₂CF₂—,—CF₂CF(CF₃)— or —CF₂CF₂CF₂— and R³ _(f) represents a linear, branched orcyclic perfluoroalkyl group having 1 to 6 carbon atoms.
 7. The method ofclaim 1 wherein the concentration of perfluorovinyl ether monomer isfrom 1 to 70 wt % of said emulsion
 8. The method of claim 1 wherein theconcentration of said fluorinated emulsifier is is from 0.1 to 4 wt % ofsaid emulsion.
 9. The method of claim 1 wherein the concentration ofsaid initiator is from 0.01 to 2 wt % of said pre-emulsion.
 10. Themethod of claim 1 wherein the temperature is from 40 to 80° C. and thetime from 6 to 48 hours.
 11. The method of claim 1 wherein the degree ofconversion of said polymerization is at least 1 percent.
 12. The methodof claim 1 wherein said fluoropolymer comprise particles having anaverage size of 50 to 200 nanometers.
 13. The method of claim 1 whereinsaid emulsifier comprises repeating units derivable from a monomer ofthe formula:

wherein s is 0, 1 or 2, and t is an integer of 2 to 4, and G is a moietycontaining one or more nonionic, anionic or cationic hydrophilic groups.14. The method of claim 1 wherein said emulsifier is selected from R_(f)^(a)—O—(CF₂O)_(k)(CF₂CF₂O)_(p)(CF(CF₃)CF₂O)_(q)-Q¹-COOM orMOOC-Q¹-O-(CF₂O)_(k)(CF₂CF₂O)_(p)(CF(CF₃)CF₂O)_(q)-Q²-COOZ wherein k, pand q each represent a value of 0 to 15, and the sum of k, p and q beingsuch that the number average molecular weight is at least 200 g/mol,R_(f) ^(a) represents a perfluoroalkyl group of 2 to 4 carbon atoms, Mand Z each independently represent hydrogen or a cation and Q¹ and Q²each independently represents —CF₂— or —CF(CF₃)—.
 15. The method ofclaim 13 further comprising an emulsifier of the formula:MOOC-Q¹-O—(CF₂O)_(k)(CF₂CF₂O)_(p)(CF(CF₃)CF₂O)_(q)-Q²-COOZ wherein k, pand q each represent a value of 0 to 15, and the sum of k, p and q beingsuch that the number average molecular weight is at least 200 g/mol,R_(f) ^(a) represents a perfluoroalkyl group of 2 to 4 carbon atoms, Mand Z each independently represent hydrogen or a cation and Q¹ and Q²each independently represents —CF₂— or —CF(CF₃)—; and
 16. The method ofclaim 1 wherein said initiator comprises a water-soluble initiator. 17.The method of claim 16 wherein said water-soluble initiator is presentin amounts from 0.01 to 2 weight percent, based on the total weight ofthe monomers.
 18. The method of claim 1 wherein the temperature of saidpolymerization step is between 50 and 80° C.
 19. The method of claim 1wherein the amount of emulsifier is from 0.01 to 15 weight percent,relative to the total weight of the monomers.
 20. The method of claim 1further comprising the step of isolating said particles ofpoly(perfluorovinyl ether) from said dispersion.
 21. Method for treatinga fibrous substrate comprising contacting the fibrous substrate with afluoropolymer dispersion of claim
 1. 22. Method according to claim 21wherein the fluoropolymer dispersion is applied to the fibrous substratein an amount such that the resulting amount of said fluoropolymer onsaid fibrous substrate is not-more than 3% by weight based on the weightof said fibrous substrate.
 23. Method according to claim 21 wherein saidfibrous substrate is textile.
 24. Method according to claim 21 whereinsubsequent to contacting said fibrous substrate with said fluorochemicalcomposition, said fibrous substrate is subjected to a heat treatmentbetween 90° C. and 170° C. for a time of 20 seconds to 10 minutes. 25.Fibrous substrate comprising on at least part of at least one surfacethereof a dispersion of claim 1 in an amount of not more than 3% byweight based on the weight of said fibrous substrate.
 26. Fibroussubstrate according to claim 25 further comprising on said part of saidat least one surface an auxiliary component capable of further improvingthe oil- and/or water repellency of the fibrous substrate or anauxiliary component that is capable of providing improved soil/stainrelease properties to the fibrous substrate.
 27. Fibrous substrateaccording to claim 26 wherein said auxiliary component is selected fromthe group consisting of aliphatic polyisocyanates, blocked isocyanates,aliphatic or aromatic carbodiimides and homo- or copolymers of alkylesters of acrylic or methacrylic acid.
 28. The method of claim 1 whereinthe concentration of perfluorovinyl ether monomer is from 20 to 40 wt. %of said emulsion